The present invention relates to a modular structure designed to accommodate one or more printed circuit boards and having to be connected to an electronic installation.
It is applicable especially but not exclusively to electronic installations of. the integrated modular avionics type, located on-board aircraft where they are likely to be subjected to harsh environmental conditions such as vibrations, sudden accelerations, shocks, moisture, etc.
A conventional modular structure comprises at least one frame which defines a volume in which a printed circuit board can be placed, this frame comprising two side walls fitted with fixation means, each one able to be fixed either to a closure plate, or to another frame.
This frame, which is generally moulded or machined, is difficult to produce with good tolerances. It is expensive to manufacture. It comprises a certain number of mouldings, notches and grooves, both on the inside and on the outside of its uprights and cross members. Such a modular structure in a frame is relatively heavy, expensive and less than satisfactory from the thermal point of view, the heat released by the electronic components of the printed circuit board having to be removed effectively for optimum operation. In addition, its weight is a handicap from the point of view of the on-board mass. It is not unusual, during maintenance operations on an aircraft, for it to have to be replaced in a few seconds and it must be able to be easily handled.
The object of the present invention is therefore more particularly to overcome these drawbacks especially of weight, cost and cooling.
In order to do this, the present invention proposes a modular structure, capable of receiving one or more printed circuit boards, which does not have a frame.
Such a modular structure is particularly simple to produce and to assemble. The printed circuit boards that it houses are held efficiently, while the structure remains light and easy to handle.
More specifically, the present invention relates to a modular structure for carrying printed circuit boards, capable of being connected to an electronic installation, comprising two cover plates placed opposite each other, contributing to defining a housing for at least one printed circuit board.
The cover plates engage one with the other by sandwiching, via a first edge, support means for one or more connection blocks and, via a second edge, support means for a locking mechanism, in order to hold the structure in a connected position, the support means for the connection blocks and for the locking mechanism having ends which are separate before assembly.
Preferably, the cover plates include an at least one other edge, stiffening means making it possible among other things to improve the engagement of the cover plates with each other.
The support means for the locking mechanism can take the form of at least one bar.
The support means for the connection blocks can take the form of at least one bar arranged so as to contribute to defining, when it is sandwiched between the two cover plates, one or more cavities open towards the outside of the housing and intended to receive the connection blocks. A connection block in a cavity is intended to be connected, on one side, to the printed circuit board and, on the other side, to another connection block, external to the structure and facing it.
The stiffening means may be formed by at least one portion making at least one change in direction relative to the main surface of the cover plate. A preferred embodiment is to use as stiffening means an angle bracket with two flanges, one a median flange and the other an end flange, these flanges making two changes in direction relative to the main surface of the cover plate.
The end flanges can be provided with holes for the purpose of assembling them.
In order to carry out proper internal ventilation of the housing, the median flanges can be provided with at least one opening for ventilation.
In order to be able to house bulky electronic components, without significantly increasing the size of the modular structure, the median flange of an angle bracket belonging to one of the cover plates can have a width different to that of an angle bracket belonging to the other cover plate.
In order to improve the holding and the stiffening of the printed circuit board, provision can be made for the structure to carry at least one stiffening rod. The results are improved if the stiffening rod is secured to one of the cover plates. Provision can also be made for the printed circuit board to carry at least one stiffening bar on each one of its faces.
In a modular structure with just one printed circuit board, the two stiffening rods can each be secured to one of the cover plates.
In a configuration with two stiffening rods carried by two different faces of the printed circuit board, it is not necessary for these rods to have the same length.
However, it is preferable that they have approximately the same orientation.
In the modular structures with many printed circuit boards, the cover plates sandwich at least one spacer, using the stiffening means.
In order to encourage good internal ventilation, it is preferable that the spacer be provided with at least one opening for ventilation.
One of the printed circuit boards is fixed to a spacer when the modular structure houses more than two printed circuit boards.
In order to guarantee satisfactory security when the modular structure is introduced into a rack, it is possible to include polarization means within the support means for the connection blocks.
Similarly, in order to facilitate positioning of the structure in the rack, it is possible to include positioning means on the support means for the connection blocks.